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Leukocyte Adhesion (leukocyte + adhesion)
Selected AbstractsLeukocyte Adhesion in Capillary-Sized, P-Selectin-Coated MicropipettesMICROCIRCULATION, Issue 2 2008Prithu Sundd ABSTRACT Objective: Leukocyte retention in lung capillaries is observed in normal physiology and following a bacterial infection. It has been hypothesized that cells either become mechanically trapped or adhere to capillary endothelial cells via adhesion molecules. We propose that retention involves both mechanical and adhesive forces and that the biochemical adhesive force is modulated by mechanical forces that alter the area of contact between leukocytes and endothelium. Methods: To probe this hypothesis, an adhesion assay has been developed in which individual HL-60 cells were aspirated into micropipettes pre-coated with P-selectin. Following aspiration, cells were exposed to physiological pressure differences. Results: Little adhesion was seen in micropipettes coated with BSA, whereas significant adhesion was observed in micropipettes coated with P-selectin. The frequency of cell arrest on P-selectin in the micropipette was much greater than on P-selectin in a parallel plate flow chamber even though the disruptive force in the micropipette assay exceeds that in the parallel plate flow chamber. These results demonstrate that receptor,ligand interactions can enhance adhesion in a capillary geometry and that differences in capillary geometry vs. venule geometry can significantly influence the adhesive phenotype. Conclusions: Taken together, these observations support the hypothesis that an interplay between mechanical and biochemical adhesive forces can play a major role in retention. [source] Platelet Recruitment in the Murine Hepatic Microvasculature During Experimental Sepsis: Role of NeutrophilsMICROCIRCULATION, Issue 2 2006GEORG SINGER ABSTRACT Objectives: Sepsis is a major clinical problem that often results in the dysfunction or failure of multiple organs, including the liver. While inflammatory cell activation has been implicated as an early critical event in sepsis-induced liver dysfunction, there is growing evidence for the involvement of activated platelets in this pathologic process. Methods: Intravital microscopy was used in this study to assess the magnitude and time course of platelet adhesion in the liver microcirculation during experimental sepsis and to determine whether the platelet accumulation is linked to leukocyte infiltration. The adhesion of platelets and leukocytes in terminal hepatic venules (THV) and sinusoids was quantified at 2, 4, and 6 h after abdominal sepsis induced by cecal ligation and puncture (CLP). Results: While the rolling and firm adhesion of platelets and leukocytes in THV were not altered in the first 2 h after CLP, platelet recruitment was observed at 4 h and further elevated at 6 h after CLP. Leukocyte adhesion in THV exhibited a similar time course. A similar accumulation of blood cells in sinusoids was noted after CLP. This was accompanied by an increased number of nonperfused sinusoids. CLP-induced leukocyte and platelet recruitment in THV and sinusoids was attenuated in mice rendered neutropenic with anti-neutrophil serum. Conclusion: These findings indicate that sepsis is associated with a neutrophil-dependent recruitment of platelets in the liver microcirculation that impairs sinusoidal perfusion and may contribute to the liver dysfunction associated with sepsis. [source] Leukocyte rolling is exclusively mediated by P-selectinin colonic venulesBRITISH JOURNAL OF PHARMACOLOGY, Issue 7 2002Ming Xiu Wan The objective of the present study was to examine the role of the endothelial selectins (i.e. P- and E-selectin) in leukocyte-endothelium interactions in colonic venules by use of intravital microscopy. Balb/c mice were exposed to dextran sodium sulphate (DSS) in the drinking water for 5 days or treated intraperitoneally (i.p.) with tumour necrosis factor-, (TNF-,) for 3 h. In DSS-treated mice, mRNA of both P- and E-selectin were expressed and leukocyte rolling and adhesion was increased to 27±3 cells min,1 and 36±8 cells mm,1, respectively. An anti-P-selectin antibody abolished DSS-induced leukocyte rolling, whereas an antibody against E-selectin had no effect. Established leukocyte adhesion was insensitive to inhibition of the selectins. DSS markedly increased production of TNF-, in the colon. TNF-, increased leukocyte rolling to 22±3 cells min,1 and adhesion to 45±4 cells mm,1. Only inhibition of P-selectin significantly reduced (>94%) leukocyte rolling provoked by TNF-,. Leukocyte adhesion was not changed by late anti-P-selectin antibody treatment. In contrast, pretreatment with the anti-P-selectin antibody not only abolished leukocyte rolling but also completely inhibited firm adhesion in response to TNF-,. This study demonstrates that P-selectin plays an important role in leukocyte rolling in colonic venules, both in experimental colitis and when stimulated with TNF-,. Moreover, P-selectin-dependent leukocyte rolling was found to be a precondition for TNF-,-induced firm adhesion. Thus, these findings suggest that P-selectin may be a key target to reduce pathological recruitment of inflammatory cells in the colon. British Journal of Pharmacology (2002) 135, 1749,1756; doi:10.1038/sj.bjp.0704638 [source] Increased circulating platelet,leukocyte aggregates in myeloproliferative disorders is correlated to previous thrombosis, platelet activation and platelet countEUROPEAN JOURNAL OF HAEMATOLOGY, Issue 3 2001Morten Krogh Jensen Abstract: Platelet,leukocyte adhesion may occur as a consequence of platelet activation and possibly plays a key role in the deposition of activated platelets and fibrin in the thrombotic plug. The aim of the present study was to assess by whole blood flow cytometry the presence of circulating platelet,leukocyte aggregates (PLA) and the platelet,leukocyte response to platelet agonist stimulation (ADP and TRAP) in 50 patients with chronic myeloproliferative disorders (MPD) and 30 controls. PLA were identified as platelet,granulocyte/monocyte aggregates (PGMA), platelet,monocyte aggregates (PMA) and defined as the percentage of leukocytes coexpressing the platelet-specific marker glycoprotein Ib. Compared to controls the mean percentage of PGMA and PMA was increased in unstimulated whole blood from patients with MPD (7.98 vs. 1.76%; p<0.001 and 12.34 vs. 3.2%; p<0.001, respectively). The percentage of PGMA was correlated to the platelet count (r=0.46; p<0.001), percentage of P-selectin (r=0.69; p<0.001) and thrombospondin (r=0.58; p<0.001) positive platelets and platelet expression of GPIV (r=0.33; p=0.02). The mean percentage of PGMA and PMA was significantly increased in ADP-stimulated whole blood of patients (57.14 vs. 47.92%; p=0.009 and 54.91 vs. 45.89%; p<0.001, respectively). Compared to patients without a history of thrombosis, patients having experienced microvascular disturbances or a thrombotic event had a higher mean percentage of PGMA and PMA in non-stimulated whole blood (10.07 vs. 6.34%; p=0.025 and 14.81 vs. 10.48%; p=0.021, respectively) and a higher percentage of PGMA in ADP stimulated whole blood (64.32 vs. 51.50%; p<0.01). These data document an increased frequency of PLA in non-stimulated whole blood in MPD associated with a previous history of thrombosis or microvascular disturbances. [source] Down-regulation of endothelial adhesion molecules and leukocyte adhesion by treatment with superoxide dismutase is beneficial in chronic immune experimental colitisINFLAMMATORY BOWEL DISEASES, Issue 10 2005Joaquim Seguí PhD Abstract Modulation of adhesion molecule expression that govern trafficking of leukocytes into the inflamed intestine is envisioned as a new strategy for treatment of inflammatory bowel disease (IBD). This study was designed to determine the impact of reducing oxidative stress on adhesion molecules expression and leukocyte recruitment in experimental chronic colitis. For that purpose, colitic interleukin-10 knockout and wild-type mice were studied. Groups of animals were treated with Cu/Zn superoxide dismutase (SOD1) 13 mg/kg/d or vehicle for either 7 or 14 days. Expression of vascular cell adhesion molecule-1 and mucosal addressin cell adhesion molecule-1 were determined; leukocyte-endothelial cell interactions in colonic venules were studied with intravital microscopy; and changes in colon pathology and biomarkers of colitis severity were determined. Development of colitis was associated with a marked increase in endothelial vascular cell adhesion molecule-1 and mucosal addressin cell adhesion molecule-1 expression, which were significantly reduced by treatment with SOD1. The increase in leukocyte rolling and adhesion in colonic venules of colitic mice were significantly reduced by administration of SOD1. This treatment markedly reduced colonic lipid hydroperoxidation, myeoloperoxidase activity, and plasma levels of serum amyloid A protein and resulted in significant, although modest, reductions in histologic damage score. The therapeutic value of SOD1 when administered prophylactically was assessed in the dextran sulfate sodium model of colitis with similar positive results. These results indicate that SOD1 affords significant amelioration of colonic inflammatory changes in experimental colitis. Down-regulation of adhesion molecule expression, reduction of lipid hydroperoxidation, and recruitment of leukocytes into the inflamed intestine contribute to this beneficial effect. [source] Butyrate inhibits leukocyte adhesion to endothelial cells via modulation of VCAM-1INFLAMMATORY BOWEL DISEASES, Issue 2 2004Thomas Menzel MD Abstract Background Leukocyte recruitment to areas of inflammation depends on Integrin-VCAM/ICAM interaction. Blocking the vascular cell adhesion molecule (VCAM-1) and the intracellular adhesion molecule (ICAM-1) may have therapeutic benefit for the inflammatory component of bowel disease. Notably, the induction of ICAM and VCAM is mediated by a nuclear factor kappaB (NF-,B)-dependent mechanism. We investigated whether the anti-inflammatory properties of butyrate are mediated via the modulation of VCAM and ICAM on human endothelial cells. Methods VCAM-1 and ICAM-1 expression on human endothelial cells upon tumor necrosis factor-, (TNF-,) stimulation was assessd by FACS analysis. A monocyte adhesion assay was performed to evaluate the relevance of a modulated CAM-expression. Electrophoretic mobility shift assays were applied to investigate NF-,B activation. Results The observed butyrate-associated inhibition of monocyte adhesion to endothelial cells is associated with an inhibition of NF-,B activation in human endothelial cells. In this context, the observed suppression of the TNF-, induced VCAM-1 expression is likely to play an essential role. Conclusions Butyrate inhibits VCAM-1 mediated leukocyte adhesion to human endothelial cells. This inhibition may contribute to the anti-inflammatory effects of butyrate in patients with distal ulcerative colitis. [source] Biocompatibility investigation and urea removal from blood by urease-immobilized HEMA incorporated poly(ethyleneglycol dimethacrylate) microbeadsJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 1 2003F. Ayhan Abstract The biocompatibility of modified and urease-immobilized poly(ethyleneglycol dimethacrylate/2-hydroxyethylmetacrylate) [poly(EGDMA/HEMA)] microbeads was tested through blood compatibility tests. Twelve percent HEMA incorporated nonporous particles of 105,125 ,m were used in the research. Hydroxyl groups on microbeads were chemically modified by following a three-step procedure that is composed of activation, spacer-arm incorporation (hexamethylene diamine) and, finally, glutaraldehyde bounding. Enzyme urease was immobilized on microbead surfaces, and adsorption of blood proteins in serum and plasma, blood coagulation time, and leukocyte and platelet adhesion were tested. Incubation of 1.5 cc of biological fluid with 100 mg of urease-immobilized poly(EGDMA/HEMA) microbeads at room temperature shows that protein adsorption on surfaces occurs, but protein content after treatment was in the range of healthy people. Adsorbed albumin and total globulin amounts per gram of microbeads is much greater than fibrinogen. Immobilization of urease reduced the protein adsorption and blood coagulation times compared with those of modified microbeads. Prothrombin time (PT) was not altered much, whereas poly(EGDMA/HEMA) microbeads induced a significant increase of activated partial thromboplastin time (APTT). The platelet and leukocyte adhesion slightly increased with the modification of poly(EGDMA/HEMA) and decreased with the introduction of urease. When blood samples were treated with urease-immobilized microbeads, BUN values of patients were lowered to almost acceptable amounts. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 64B: 13,18, 2003 [source] P-selectin mediates leukocyte rolling in concanavalin-A-induced hepatitisLIVER INTERNATIONAL, Issue 5 2005Sandra March Abstract: Concanavalin- A (Con-A)-induced hepatitis is an experimental model of human autoimmune hepatitis characterized by leukocyte activation and infiltration of the liver. The aim of the present study was to evaluate the role of P-selectin on leukocyte,endothelial interactions within the hepatic microvasculature in response to Con-A. Methods: The study was performed in P-selectin-deficient mice and wild-type mice pretreated with anti-P-selectin blocking monoclonal antibody (mAb) or vehicle. After 2 h of Con-A (20 mg/kg i.v.) or PBS administration, leukocyte rolling and adhesion and the index of sinusoidal perfusion were evaluated using the intravital microscopy technique in the liver. Apoptosis was determined by flow cytometry analysis of caspase-3 activity assayed on freshly isolated hepatocytes. Results: Con-A induced a significant increase in leukocyte rolling, mainly located at the central venule (2.1±0.4 vs 0.6±0.2 cells/min in wild-type mice treated with vehicle) and less marked, but still significant, in portal venules. This was associated with a significant increase in leukocyte adhesion. In P-selectin-deficient mice treated with Con-A, leukocyte rolling in portal and central venules was markedly reduced. However, leukocyte adhesion was only partially attenuated. A few sinusoids were perfused in wild-type mice treated with Con-A (26%). The percentage of perfused sinusoids was significantly higher in P-selectin-deficient mice (45%; P<0.05 vs wild-type). Similar effects were noted after the simultaneous injection of Con-A and anti-P-selecting mAb in wild-type mice. After Con-A treatment, apoptosis was markedly reduced in isolated hepatocytes of P-selectin-deficent mice (37±7% vs 75±5% in wild type). Conclusion: The results of this intravital microscopy study clearly demonstrate that P-selectin is involved in the initial leukocyte rolling that leads to the development of Con-A-induced liver injury. [source] A Separate Role for ICAM-1 and Fluid Shear in Regulating Leukocyte Interactions with Straight Regions of Venular Wall and Venular ConvergencesMICROCIRCULATION, Issue 6 2009RONEN SUMAGIN ABSTRACT Objective: Variation in expression of adhesion molecules plays a key role in regulating leukocyte behavior, but the contribution of fluid shear to these interactions cannot be ignored. Here, we dissected the effects of each of these factors on leukocyte behavior in different venular regions. Materials and Methods: Leukocyte behavior was quantified in blood-perfused microvascular networks in anesthetized mouse cremaster muscle, using intravital confocal microscopy. ICAM-1 expression and fluid shear rate were quantified by using ICAM-1 fluorescent labeling, fluorescent particle tracking, and computational fluid dynamics. Results: Tumor necrosis factor alpha induced an increase in ICAM-1 expression and abolished the differences observed among control venules of different sizes. Consequently, leukocyte adhesion was increased to a similar level across all vessel sizes [5.1±0.46 leukocytes/100 ,m vs. 2.1±0.47 (control)], but remained significantly higher in venular convergences (7.8±0.4). Leukocyte transmigration occurred primarily in the smallest venules and venular convergences (23.9±5.1 and 31.9±2.7 leukocytes/10,000 ,m2 tissue, respectively). In venular convergences, the two inlet vessels are predicted to create a region of low velocity, increasing leukocyte adhesion probability. Conclusions: In straight regions of different-sized venules, the variability in ICAM-1 expression accounts for the differences in leukocyte behavior; in converging regions, fluid shear potentially has a greater effect on leukocyte endothelial cell interactions. [source] Inflammatory and Hemodynamic Changes in the Cerebral Microcirculation of Aged Rats after Global Cerebral Ischemia and ReperfusionMICROCIRCULATION, Issue 4 2008Leslie Ritter ABSTRACT Effects of aging on inflammation and blood flow in the brain are unclear. Young (three to six months) and aged (19,22 months) male Brown Norway Fisher rats were used to compare (i) leukocyte function in nonischemic conditions and (ii) leukocyte function and hemodynamic changes after ischemia-reperfusion (I-R). In nonischemic studies, polymorphonuclear (PMN) CD11b expression and reactive oxygen species (ROS) production were measured with flow cytometry and PMN chemotaxis was measured with a Boyden chamber (+/-fMLP). In I-R studies, ischemia was induced by bilateral carotid artery occlusion and hypotension (20 minutes). During early reperfusion (30 minutes), leukocyte adhesion and rolling and blood-shear rates were measured using fluorescence microscopy. During late reperfusion (48 hours), mortality, neurological function, and leukocyte infiltration were measured. Stimulated PMN chemotaxis was increased in nonischemic aged rats (p < 0.05). In early reperfusion, there was a significant increase in leukocyte rolling and adhesion in the cerebral microcirculation and a significant decrease in shear rate in aged rats, compared to the young (p < 0.05). During late reperfusion, neurologic function was worse in aged vs. young rats (p < 0.05). These findings suggest that increased intravascular PMN adhesion and vascular dysfunction may contribute to poor neurologic outcome after cerebral I-R in the aged brain. [source] Microvascular Rheology and HemodynamicsMICROCIRCULATION, Issue 1 2005HERBERT H. LIPOWSKY ABSTRACT The goal of elucidating the biophysical and physiological basis of pressure,flow relations in the microcirculation has been a recurring theme since the first observations of capillary blood flow in living tissues. At the birth of the Microcirculatory Society, seminal observations on the heterogeneous distribution of blood cells in the microvasculature and the rheological properties of blood in small bore tubes raised many questions on the viscous properties of blood flow in the microcirculation that captured the attention of the Society's membership. It is now recognized that blood viscosity in small bore tubes may fall dramatically as shear rates are increased, and increase dramatically with elevations in hematocrit. These relationships are strongly affected by blood cell deformability and concentration, red cell aggregation, and white cell interactions with the red cells and endothelium. Increasing strength of red cell aggregation may result in sequestration of clumps of red cells with either reductions or increases in microvascular hematocrit dependent upon network topography. During red cell aggregation, resistance to flow may thus decrease with hematocrit reduction or increase due to redistribution of red cells. Blood cell adhesion to the microvessel wall may initiate flow reductions, as, for example, in the case of red cell adhesion to the endothelium in sickle cell disease, or leukocyte adhesion in inflammation. The endothelial glycocalyx has been shown to result from a balance of the biosynthesis of new glycans, and the enzymatic or shear-dependent alterations in its composition. Flow-dependent reductions in the endothelial surface layer may thus affect the resistance to flow and/or the adhesion of red cells and/or leukocytes to the endothelium. Thus, future studies aimed at the molecular rheology of the endothelial surface layer may provide new insights into determinants of the resistance to flow. [source] Inhibition of Leukocyte Adherence Enables Venular Control of Capillary Perfusion in Streptozotocin-Induced Diabetic RatsMICROCIRCULATION, Issue 8 2004KAVITHA NELLORE ABSTRACT Objective: Vasoactive molecules can diffuse from venules to dilate closely paired arterioles and enhance capillary perfusion. Venular control of capillary flow has been found to be dependent on nitric oxide (NO), which might be scavenged rapidly in diabetic microvasculature due to the presence of activated leukocytes. This study attempts to improve venular control of capillary flow using fucoidan, which inhibits venular leukocyte adhesion. Methods: Microvascular red blood cell velocity was measured in the mesentery of streptozotocin-induced diabetic rats, with and without fucoidan treatment, and in normal rats. Arteriolar pathways leading to branching capillaries were videotaped to measure the percent of the surrounding area occupied by a venule (% pairing). Microvascular wall NO was measured using fluorescent diaminofluorescein-2-diacetate in diabetic rats, with and without fucoidan treatment. Results: In normal rats, close pairing of venules to arterioles resulted in faster capillary flow. However, after 4,5 weeks of diabetes, the correlation between capillary velocity and % pairing was no longer significant. Capillary velocity and % pairing decreased , 50% in comparison to normal rats. Treatment of diabetic rats with fucoidan restored venular control of capillary flow and increased NO levels. Conclusion: Leukocyte-derived mediators that scavenge NO may lead to inadequate venular control of capillary flow in diabetes. [source] Experimental Models To Investigate Inflammatory Processes in Chronic Venous InsufficiencyMICROCIRCULATION, Issue S1 2000RONALD J. KORTHUIS ABSTRACT Chronic venous insufficiency (CVI) is characterized by leukocyte adhesion and infiltration, venous hypertension and dilatation, and valvular dysfunction. The fact that activated white cells can direct a powerful cytotoxic arsenal at parenchymal cells following their extravasation into the tissues led to the original proposal that leukocytes may play a causative role in the pathogenesis of venous disease. A large body of subsequent work indicates that white blood cells are indeed activated in CVI. However, identification of the factors responsible for initiating leukosequestration and activation in such disorders and determination of whether these activated cells then contribute to the progression of venous disease have been hampered by the lack of appropriate animal models that accurately mimic the human condition. Tantalizing evidence suggesting that cyclical periods of ischemia and reperfusion (I/R) may occur in diseased regions of the skin is beginning to accumulate. As is the case with CVI, leukocyte infiltration is a prominent feature in I/R and activated neutrophils play a causative role in the reperfusion component of tissue injury via the targeted release of reactive oxygen metabolites and hydrolytic enzymes. In light of these considerations, many investigators have suggested that examining the mechanisms of I/R injury in skin and skeletal muscle, where ischemia is produced by arterial occlusion, may provide a relevant model for studying the pathogenesis of CVI. Others have suggested that venous occlusion may represent a more appropriate model, as this approach also produces the venous hypertension that is characteristic of the disease. The purpose of this review is to summarize the evidence pointing to the involvement of I/R and venous hypertension as causative factors in CVI-induced leukocyte recruitment. In addition, we will describe the evidence in favor of the view that white blood cells contribute to the pathogenesis of CVI. Finally, we will describe several different experimental models that have been used to examine the role of I/R-induced microvascular dysfunction as it may pertain to the development of CVI, together with a discussion of the relative advantages and limitations of the various models. [source] Effect of HTK on the microcirculation in the rat cremaster muscle during warm ischemia and reperfusionMICROSURGERY, Issue 2 2005Jacqueline Bastiaanse M.D. Histidine-tryptophan-ketoglutarate (HTK) preserves rat muscle function during cold storage. We examined the effect of HTK perfusion on preservation of microvascular function during 4 h of warm ischemia and subsequent reperfusion (I/R) in the rat cremaster muscle. Leukocyte-endothelium interactions, capillary perfusion, and arteriole diameters were quantified prior to HTK-perfusion and/or ischemia, and at 0, 1, and 2 h after restoration of blood flow. In all groups, the number of rolling leukocytes increased with time, whereas I/R induced a slight increase in leukocyte adhesion. After ischemia, capillary perfusion rapidly recovered to about 50% and returned to near normal (90%) after 2 h. HTK at 22°C did not affect the assessed microcirculation variables, whereas HTK at 4°C reduced leukocyte rolling, but not adhesion. Therefore, microvascular function of HTK-perfused muscles was not better preserved during warm I/R than that of nonperfused muscles. Contrary to other preservation solutions, HTK perfusion in itself was not detrimental to the microcirculation. © 2005 Wiley-Liss, Inc. Microsurgery 25:174,180, 2005. [source] The Role of Amniotic Fluid Interleukin-6, and Cell Adhesion Molecules, Intercellular Adhesion Molecule-1 and Leukocyte Adhesion Molecule-1, in Intra-Amniotic InfectionAMERICAN JOURNAL OF REPRODUCTIVE IMMUNOLOGY, Issue 5 2000CHAUR-DONG HSU PROBLEM: To determine amniotic fluid concentrations and correlations of interleukin-6 (IL-6), intercellular adhesion molecule-1 (ICAM-1), and leukocyte adhesion molecule-1 (LAM-1) in patients with and without intra-amniotic infection. METHOD OF STUDY: Fourteen specimens with intra-amniotic infection and 45 without intra-amniotic infection were studied. Intra-amniotic infection was defined as the presence of a positive amniotic fluid culture. Amniotic fluid IL-6, ICAM-1, and LAM-1 levels were determined by an enzyme-linked immunoassay, and normalized by amniotic fluid creatinine levels. RESULTS: Amniotic fluid concentrations of IL-6 and LAM-1 were significantly higher in patients with than without intra-amniotic infection. However, amniotic fluid ICAM-1 concentrations were not significantly different between two groups. Amniotic fluid IL-6, LAM-1, and ICAM-1 were positively correlated. CONCLUSIONS: Our data indicate that amniotic fluid IL-6 is significantly associated with an increased adhesion molecule expression in intra-amniotic infection. However, LAM-1 plays a more important role than ICAM-1 in intra-amniotic infection. [source] Junctional adhesion molecule C mediates leukocyte adhesion to rheumatoid arthritis synoviumARTHRITIS & RHEUMATISM, Issue 10 2008Bradley J. Rabquer Objective Leukocyte infiltration into the rheumatoid arthritis (RA) synovium is a multistep process in which leukocytes leave the bloodstream and invade the synovial tissue (ST). Leukocyte transendothelial migration and adhesion to RA ST requires adhesion molecules on the surface of endothelial cells and RA ST fibroblasts. This study was undertaken to investigate the role of junctional adhesion molecule C (JAM-C) in mediating leukocyte recruitment and retention in the RA joint. Methods Immunohistologic analysis was performed on RA, osteoarthritis (OA), and normal ST samples to quantify JAM-C expression. Fibroblast JAM-C expression was also analyzed using Western blotting, cell surface enzyme-linked immunosorbent assay, and immunofluorescence. To determine the role of JAM-C in leukocyte retention in the RA synovium, in vitro and in situ adhesion assays and RA ST fibroblast transmigration assays were performed. Results JAM-C was highly expressed by RA ST lining cells, and its expression was increased in OA ST and RA ST endothelial cells compared with normal ST endothelial cells. JAM-C was also expressed on the surface of OA ST and RA ST fibroblasts. Furthermore, we demonstrated that myeloid U937 cell adhesion to both OA ST and RA ST fibroblasts and to RA ST was dependent on JAM-C. U937 cell migration through an RA ST fibroblast monolayer was enhanced in the presence of neutralizing antibodies against JAM-C. Conclusion Our results highlight the novel role of JAM-C in recruiting and retaining leukocytes in the RA synovium and suggest that targeting JAM-C may be important in combating inflammatory diseases such as RA. [source] A peptide from thrombospondin 1 modulates experimental erosive arthritis by regulating connective tissue growth factorARTHRITIS & RHEUMATISM, Issue 8 2006Joanne M. Manns Objective Rheumatoid arthritis (RA) is a chronic inflammatory disease associated with leukocyte adhesion to and extravasation through vascular endothelium into synovial tissue. Recent evidence indicates that the thrombospondin 1 gene is up-regulated in patients with RA. We have identified a region within the TSP-1 type 3 repeats that inhibits human neutrophil elastase (HNE) and binds to human neutrophils. The present study was undertaken to investigate the therapeutic benefit of this TSP-1,derived peptide sequence and its effect on connective tissue growth factor (CTGF), a protein involved in fibrotic disorders and in neovascularization, which is a hallmark of RA. Methods CTGF gene and protein expression, as well as protein levels of CTGF in the synovium, after treatment with the TSP-1,derived peptide were studied in the peptidoglycan,polysaccharide animal model of erosive arthritis. Results Peptide treatment prevented joint infiltration and inflammation and was associated with reduced circulating antigen levels of HNE and TSP-1. Additionally, CTGF was up-regulated in this experimental model of RA. Treatment with the TSP-1,derived peptide was associated with down-regulation of the message and protein levels of CTGF. Immunofluorescence studies showed that the mean area fraction of CTGF immunoreactivity in the peptide-treated group of animals was significantly less than that in the untreated group. Conclusion These results document a role for TSP-1 in regulating CTGF gene and protein expression in synovial tissue, suggesting a link with the disease course in this model of RA. This TSP-1,derived synthetic peptide may represent an important template for drug development in RA and other inflammatory conditions associated with neutrophil activation. [source] Lymphocyte function antigen-1 mediates leukocyte adhesion and subsequent liver damage in endotoxemic miceBRITISH JOURNAL OF PHARMACOLOGY, Issue 4 2004Xiang Li Sepsis is associated with leukocyte activation and recruitment in the liver. We investigated the role of lymphocyte function antigen-1 (LFA-1) in endotoxin-induced leukocyte,endothelium interactions, microvascular perfusion failure, hepatocellular injury and apoptosis in the liver by use of gene-targeted mice, blocking antibodies and a synthetic inhibitor of LFA-1 (LFA703). For this purpose, mice were challenged with lipopolysaccharide (LPS)+D -galactosamine (Gal), and intravital microscopy of the liver microcirculation was conducted 6 h later. The number of firmly adherent leukocytes in response to LPS/Gal was reduced by 48% in LFA-1-deficient mice. Moreover, endotoxin-induced increases of apoptosis and enzyme markers of hepatocellular injury were decreased by 64 and 69,90%, respectively, in LFA-1-deficient mice. Furthermore, sinusoidal perfusion was improved in endotoxemic mice lacking LFA-1. A similar protective pattern was observed in endotoxemic mice pretreated with an antibody against LFA-1. Thus, immunoneutralization of LFA-1 reduced endotoxin-induced leukocyte adhesion by 55%, liver enzymes by 64,66% and apoptosis by 42%, in addition to the preservation of microvascular perfusion. Administration of a novel statin-derived inhibitor of LFA-1, LFA703, significantly decreased leukocyte adhesion (more than 56%) and the subsequent liver injury in endotoxemic mice. Thus, this study demonstrates a pivotal role of LFA-1 in supporting leukocyte adhesion in the liver. Moreover, interference with LFA-1-mediated leukocyte adhesion protects against endotoxemic liver damage, and may constitute a potential therapeutic strategy in sepsis. British Journal of Pharmacology (2004) 141, 709,716. doi:10.1038/sj.bjp.0705634 [source] Leukocyte rolling is exclusively mediated by P-selectinin colonic venulesBRITISH JOURNAL OF PHARMACOLOGY, Issue 7 2002Ming Xiu Wan The objective of the present study was to examine the role of the endothelial selectins (i.e. P- and E-selectin) in leukocyte-endothelium interactions in colonic venules by use of intravital microscopy. Balb/c mice were exposed to dextran sodium sulphate (DSS) in the drinking water for 5 days or treated intraperitoneally (i.p.) with tumour necrosis factor-, (TNF-,) for 3 h. In DSS-treated mice, mRNA of both P- and E-selectin were expressed and leukocyte rolling and adhesion was increased to 27±3 cells min,1 and 36±8 cells mm,1, respectively. An anti-P-selectin antibody abolished DSS-induced leukocyte rolling, whereas an antibody against E-selectin had no effect. Established leukocyte adhesion was insensitive to inhibition of the selectins. DSS markedly increased production of TNF-, in the colon. TNF-, increased leukocyte rolling to 22±3 cells min,1 and adhesion to 45±4 cells mm,1. Only inhibition of P-selectin significantly reduced (>94%) leukocyte rolling provoked by TNF-,. Leukocyte adhesion was not changed by late anti-P-selectin antibody treatment. In contrast, pretreatment with the anti-P-selectin antibody not only abolished leukocyte rolling but also completely inhibited firm adhesion in response to TNF-,. This study demonstrates that P-selectin plays an important role in leukocyte rolling in colonic venules, both in experimental colitis and when stimulated with TNF-,. Moreover, P-selectin-dependent leukocyte rolling was found to be a precondition for TNF-,-induced firm adhesion. Thus, these findings suggest that P-selectin may be a key target to reduce pathological recruitment of inflammatory cells in the colon. British Journal of Pharmacology (2002) 135, 1749,1756; doi:10.1038/sj.bjp.0704638 [source] NMR solution structure of a potent cyclic nonapeptide inhibitor of ICAM-1-mediated leukocyte adhesion produced by homologous amino acid substitutionCHEMICAL BIOLOGY & DRUG DESIGN, Issue 4 2004L.O. Sillerud Abstract:, We have previously described a disulfide-linked cyclic nonapeptide (inhibitory peptide-01, IP01), with the sequence CLLRMRSIC, which binds to intercellular adhesion molecule-1 (ICAM-1), and blocks binding to its counter-structure, the integrin ,L,2 (leukocyte functional antigen-1, LFA-1) (Sillerud et al., J. Peptide Res. 62, 2003: 97). We now report the optimization of this peptide by means of single homologous amino acid substitutions to yield a new peptide (IP02-K6; CLLRMKSAC) which shows an approximately sixfold improvement in inhibitory activity of multivalent leukocyte binding (inhibition constant for 50% inhibition, IC50 = 90 ,m) compared with IP01 (IC50 = 580 ,m). This improvement in activity gives IP02-K6 potent in vivo activity in a murine model of ischemia reperfusion injury (Merchant et al., Am. J. Physiol. Heart Circ. 284, 2003: H1260). In order to determine the structural features relevant to ICAM-1-binding, we have determined the structure of IP02-K6 using proton nuclear magnetic resonance (NMR) spectroscopy and restrained molecular modeling. In our previously reported study of solution models of IP01, we observed three interconverting conformations during low-temperature molecular dynamics simulation. In the present study, we find a single conformation of IP02-K6 similar to one of the previously found conformations of IP01 (family C). In particular, an R4-S7 , -turn is present in similar proportions in both conformation C of IP01 and in IP02-K6; this motif is important in binding to ICAM-1 because this turn enables the IP02-K6 backbone to drape over proline-36 on ICAM-1. The NMR-derived solution model of IP02-K6 was found to dock at the ,L,2 -binding site on ICAM-1 with no changes in peptide backbone conformation. This docking model displaced five of the 15 ,L,2 residues at the ICAM-1-binding site and provided a rationale for understanding the quantitative relationship between IP02-K6 structure and biologic activity. [source] Vascular cell adhesion molecule-1 and intercellular adhesion molecule-1 serum level in patients with chest pain and normal coronary arteries (syndrome X)CLINICAL CARDIOLOGY, Issue 4 2001Dimitris Tousoulis M.D., Ph.D. Abstract Background: Plasma levels of soluble vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (IC AM-1) mediators of leukocyte adhesion to vascular endothelium may implicate in the pathogenesis of the syndrome of chest pain with normal coronary arteries. Hypothesis: We attempted to determine whether markers of endothelial activation are raised in patients with chest pain and normal coronary arteries. Methods: We measured plasma VCAM-1, ICAM-1 (ng/ml) in 36 patients (34 men, 2 women, aged 62 ± 9 years) with stable angina, coronary artery disease (CAD), and a positive response to exercise test; in 21 patients (6 men, 15 women, aged 56 ± 9 years) with chest pain and normal coronary arteriograms (syndrome X); and in 11 healthy control subjects (8 men, 3 women, aged 49 ± 14 years). Results: Plasma ICAM-1 levels were significantly higher both in patients with CAD (mean ± standard error of the mean) (328 ± 26, p<0.05), and in syndrome X (362 ± 22, p<0.01) than in controls (225 ± 29). VCAM-1 levels were also higher in syndrome X (656 ± 42 ng/ml) and in patients with CAD (626 ± 42 ng/ml) than in controls (551 ± 60, p=0.09). Conclusions: ICAM-1 and VCAM-1 levels are increased both in patients with CAD and with syndrome X compared with control individuals. These findings may suggest the presence of chronic inflammation with involvement of the endothelium in patients with anginal chest pain and normal coronary angiograms. [source] Rickettsia prowazekii infection of endothelial cells increases leukocyte adhesion through ,v,3 integrin engagementCLINICAL MICROBIOLOGY AND INFECTION, Issue 2009Y. Bechah No abstract is available for this article. [source] | |||||||||||||